Carburetor



Sept. 27, 1932 L. D. BOYCE 1,879,053

CARBURETOR Filed July .3, 1929 2 Sheets-Sheet 1 Patented Sept. 27, 1932 LEONARD I). BOYCE, OF MAPLEWOOD; MISSOURI, ASSIGNOR TO CARTER CARBURETOR CORPORATION, OF ST. LOUIS, MISSOURI, A CORPORATION OF DELAWARE CARBURETOR Application filed July 3, 1929. Serial No. 375,602.

This application relates to carburetors and particularly to devices for varying the proportions of fuel and air delivered with a view to producing a carburetor which is adjustable to supply a suitable mixture for starting under extremely low temperature conditions as well as for normal operation. In carburetors of this general type, it has been customary to provide primary and secondary air passages, the primary leading through a primary mixing chamber standpipe or choke tube to the main mixing chamber, and the secondary leading directly-into the main mixing chamber. The main fuel supply ordih narily discharges into the choke tube in which it is mixed with the primary air, forming a comparatively rich mixture, which is diluted by the secondary air in the main mixing chamber.

The general type of carburetors to whichthis invention relates includes two classes known as plain tube and air valve carburetors. The invention in its broader aspects is applicable to both of these types of carburetors, but I have shown it in connection with a plain tube carburetor, and certain more specific features of the invention are especially adapted for use with plain tube carburetors. It will be understood by thoseskilled in the art that, the term air valve carburetor implies a suction operated spray carburetor having one or more air passages which are normally closed by a suction operated valve, this valve usually controlling the so-called auxiliary air passage which does not usually enclose the main jet of the car-- buretor. The term plain tube carburetor will be understood to imply one in which no suction operated valve is employed under normal operating conditions, although such a valve may be used, as in the case of the present invention, for operation under abnorair inlets may be restricted or out 01f, whereby the suction developedby the engine will be more efi'ective to draw fuel from the main or other jets and less effective to draw air from the atmosphere, thus producing a mixture having a high proportion of fuel for starting purposes or for operation under extremely low temperature conditions.

It is another object of this invention to provide means for partially relieving the restriction of the air passages upon a sudden increase in the suction produced by the engine such as would be occasioned by the engine beginning to run under its own power after being operated at a comparatively low speed by the starting means. It will be understood by those skilled in the art that the high restriction of the air passages, which is des rable for starting the engine at extremely low temperatures and at the very low speeds produced by the usual starting means,- would be entirely too rich for operation when the engine is running under its own power at a considerably higher speed.

Ordinary automobile engines are lubricated with an oil which varies in viscosity with the temperature, and a suitable oil for ordinary operating conditions is so heavy that the engines are very difficult to operate under low temperature conditions. The usual electric starting devices are often incapable of turning over the engine at a speed of more than twenty-five or thirty revolutions per minute. At the same time, the lowest operating speed of such engines, when running under their own power, is often two or three hundred revolutions per minute or approximately ten times the speed at which the enginemust start to fire.

The invention can be better understood upon reference to the accompanying drawings, referring to which:

Figure 1 shows a sectional elevation of the carburetor constructed according to my invention.

Figure 2 shows a sectional elevation of the carburetor shown in Figure 1 with the parts in a different operating position, the scale being slightly smaller than in Figure 1.

Figure 3 shows a sectional elevation of a standpipe, choke cone, and associated parts for a carburetor constructed according to my invention, the scale being larger than that in Figure 2 to illustrate the parts more clearly.

Figure 4 is a sectionah elevation of the parts shown in Figure 3 taken along the line 4-4 of Figure 3, looking in-the direction of the arrows.

Figure 5 is a sectional plan view taken along the line 5--5 of Figure 3.

Figure 6 is a plan View of t-he parts shown in Figure 3.

Figures 7 8, and 9 are different views of the valve for controlling the admission of air to the primary venturi.

The reference numeral 1 indicates a casting forming the main body member of the carburetor. This casting forms the walls of an air chamber 2 to which air is admitted through an air horn 3; an annular opening 4 in the upper part of the casting is arranged to receive aflanged member 5 having an extension 6 snugly fitted into the opening; the member 5 is provided with a suitable flange 7 which, with the screws 8, serves as means to attach the flange member to the main body .body member also has a downwardly extending portion 15 to which the bowl is attached by a screw 16, as shown. The fuel is supplied to the bowl by conventional means (not shown) and maintained at a constant level therein by the usual float 17 The upper part of the extension 15 is provided with a recess 18 from which a passageway 19 extends downwardly to the end of the extension where it is closed by the screw 16. This passageway communicates with the fuel bowl through an opening 20. The main jet conduit 21 is screwed by means of suitable threads into the passageway 19 and extends upwardly into the recess 18. A standpipe 22 having a suitable flange and screw threads 23 is threaded into the lower part of the recess 18 and the lower part of the standpipe surrounds the upper part of the main jet 21. v

A small port 24 permits communicatlon from the chamber 2 through the recess 18 to the accelerating well 19. The upper part of the jet 21 is loosely surrounded by an annularmember 25 which is tightly fitted into the flange 23 ofthe standpipe, the restricted space between the bore of the .member 25 and the wall of the jet 21 serving as a communication between the passageway 19 and the standpipe 22.

A port 26 formed in the wall of the standpipe permits communication between the recess 18 and the interior of the pipe. Just above this port and approximately at the levelof the upper part of the jet 21, a restricted passage 27 is formed in the standpipe to give a Venturi effect. Small ports 28.

are formed in the wall of the jet 21 and serve to bleed air from the accelerating well 19 into the jet under certain operation conditions.

The standpipe terminates at or near the restricted portion of the main venturi, as indicated. The usual throttle 29, mounted on the shaft 30, controls the flow of mixture from the carburetor. The flow of air into the main mixing chamber 31 is controlled by a choke cone assembly 32 hereinafter more fully ,described.

A manually operable shaft 33 is rotatably mounted in the walls of the casting 1 and has fixed thereto an arm 34 having a yoke to engage an annular recess 35 in the lower part of the choke cone 32. In order to give the cone a more positive closure, it is provided with a skirt 36 near its lower end of larger diameter than the restricted portion of the venturi.

Adjacent to the throttle 29, I provide a bleed opening 38 to admit air and gasoline at idling speeds. The air enters through a port 39 in the screw 40 which cooperates with the boss 41 to adjust the amount of air admitted. A small bore 42 is drilled in the flanged member 5 and is fitted with a small tube 43, this tube being made as small as possible and located at the side of the air chamber opposite the air inlet 3 to restrict the flow of air as little as possible. The tube is rolled down at some point between the opening 45 and its upper end as shown to form a highly restricted portion which serves to calibrate the amount of fuel passingthrough the tube.

A small air bleed 45 below the restriction is provided. The tube extends into a bore 46 in the extension 15 and receives fuel from the passageway 19 through a bore 47 which is formed for that purpose.

A choke operating shaft 33 is provided with a suitable operating arm 50. The throttle shaft 30 is also provided with suitable means, such as an arm 51, for operating the throttle, and interconnecting means for causing the throttle to open slightly when the choke is closed may be provided, if desired. One form of device for accomplishing this result is shown herein comprising a crank 52 fixed to the shaft 33, a second crank 53 fixed to the shaft 30, and a connecting rod 54 having an end pivotally attached to each of the cranks. The connecting rod is slotted, as at 55, to permit some lost motion with respect to the crank 52, whereby the throttle valve 29 may be freely opened to its fullest extent, irrespective of the position of the choke. The crank pin 56 on the crank 52 .is so located that in fully closing the choke the crank pin will just pass the lower dead center while the crank pin 57 on the crank 53 is so located that when the choke is fully closed and the lost mo ion in the connecting rod taken up the crank pin 57 will be approximately halfway between dead centers. This arrangement is made for the purpose of causing the throttle to slightly open when the choke is only partially closed without causing the throttle to be forced open to any great extent by fully closing the choke. It will be obvious that this is accomplished by locating the crank pin on the choke shaft in a position of minimum ratio of linear connecting rod movement to an angular crank movement, while the crank pin on the throttle shaft is located in a position of maximum ratio of linear connecting rod movement and to angular movement of the throttle shaft. I

The choke cone assembly 32 comprises the body member 58 which is slidably mounted on the standpipe and provided with the collar 35 which is engaged by the yoke on the arm 34. By-pass holes 59 are formed in the choke so that when the choke is closed against the end of the main venturi 12, a small amount of air may be permitted to by-pass under certain conditions. An annular valve member 60 is mounted on the choke in a position to close the inner ends of the passages 59. A suitable sheet metal casing 61 is provided for enclosing the valve 60 and the valve spring 62. The casing 61 is provided with a number of ports 63, as shown, to permit the air passing the valve 60 to enter the main mixing chamber 31. The spring 62 is comparatively light and is calibrated to open under the suction produced by the engine when the choke is fully closed and when the engine is operated under its ownpower. On the other hand, the spring 62 has suificient strength to close the valve 60 against any suction likely to be produced by turning the engine over at a comparatively slow speed as, for instance, with an electric starting device. The admission of air to the primary mixing chamber through the ports 26 is controlled by the valve 64. This valve which is stamped from sheet metal is longitudinally movable in the ports 26 and loosely surrounds the main nozzle 21 so that a small amount of air can enter, even when the valve 64 is fully closed. The valve is provided with a pair of extensions 65 which pass upwardly through the ports 26 and which are bent in again as at 66 to fit into and be guided by a ,pair of suitable longitudinal gooves or keyways 67 formed in the standpipe 22. A spring 68 supported at its lower end by the annular member 25 tends to hold the valve 64 in closed 'position.

The choke is counterbored at 69 to receive a light spring 70, the upper end of which is held in position by the choke, and the lower end of which normally tends to open the valve 64. The spring 70 is so calibrated and of such normal length in its unstressed position that when the choke is in its closed or upward position, the spring 7 0 will exert a comparatively small amount of pressure on the valve 64, permitting it to close under the pressure of the spring 68 which is weaker than the spring 70. In'other Words, the arrangement is such that when the choke is open to any substantial extent, the valve 64 will be fully open, but the latter valve will fully close during the final stages of the closing movement of the choke.

The standpipe is provided with one or more ports 71 which are open to the air chamber 2 when the choke is fully open, as shown in Figure 2. These ports are closed by the choke itself when it is moved to partially closed position, as shown in Figure 3, and when the choke is fully closed, as shown in Figure 4, so that the counterbore 69 would normally permit communication bctweenthe ports and the air chamber, these ports are closed by a bushing 72 which is provided with a flange 73 upon which the spring 70 seats at its upper end.

The operation ofthe device is as follows:

When it is desired to start the motor under low temperature conditions, the choke lever 50 is moved to the position shown in Figure 1, thereby raising the choke until the skirt 36 is in contact with the lower end of the main venturi 12. The upward or closing movement of the choke closes the small ports 71 in the 4 amount which is drawn in through the ports 24, the bleed port 45, the small crevice between .the valve 64 and the periphery of the main jet, and slightleakages.

The closing movement of the choke takes up the lost motion in the link 54 and causes the throttle to at least slightly open so that any suction developed by the engine will be communicated to the main jet. The level of the fuel in the float chamber is substantially as indicated by the line AA. Upon operating the engine at a low speed, as bythe usual starting means, a slight suction is developed which draws air in through the ports 24 and 45, and a. very small amount through the port 26 and valve 64. The slight suction which is created raises the level of the fuel in the main jet causing it to overerating well 19 atomizing and vaporizing the 1 The I tion would tend to form a much richer mixture than would be suitable for operating the engine under its own power, unless some additional means were provided for instantly relieving the suction to a certain extent when the engine first begins to fire. This means is present in the valve'63 and the spring 62, for it is so adjusted as to permit the valve to open instantly when the engine begins to fire of its own accord.

After the engine has been running fora brief period so that it is slightly warmed up, the choke is opened to an extentdepending on the temperature of the atmosphere and of the engine. This, opening movement of the choke automatically closes the valve 60, for it is no longer exposed to greatly different pressures on its opposite sides. The first stages of the opening movement of the choke fully opens the valve 64, permitting air to enter through the venturi 27, mixing with and partially atomizing the fuel from the main jet, and forming a rich mixture in the primary mixing chamber 76, which discharges into the main mixing chamber 31 where it is diluted with and more completely atomized by air entering through the secondary inlet port, which comprises the annular opening between the upper end of the standpipe 22 and the restricted portion or throat of the main venturi 1112. v

I claim 2- 1. In a carburetor, means forming a mixing chamber, means forming primary and secondary air passages conveying air to said chamber, a fuel jet in said primary air passage, normally open valve means for control ling the admission of air to both of said passages, a single lever for operating said valve means, said valve means being constructed and arranged to close the primary air passage during the latter part of the clos-' ing movement of the control valve for the secondary air passage, and to open the control valve for said primary air passage during the first part of the opening movement of the control valve for the secondary air passage. a

2. In a plain tube carburetor, means forming normally open primary and secondary air passages, means forming a main mixing chamber receiving air from both of said passages, means for temporarily controlling said passages comprlsing choke valves, a fuel nozzle in one of said passages between the control means for that passage and the main mixing chamber, a throttle valve controlling the outlet of said mixing chamber, a fuel passage discharging adjacent said throttle valve, said last named fuel passage having a connecti on to receive air, said connection being unaffected by the position of the said choke valves, and suction operable means for admitting additional air to said mixing chamber when said choke valves are closed.

3. In a carburetor, means forming a main mixing chamber, means forming primary and secondary air passages leading to said mixing chamber, said passages being normally open, manually operated means for closing said passages for starting purposes, and a reliefvalve opening into said mixing chamber and operable by suction when said passages are closed to admit air to the chamber when said valves are closed.

4. In a plain tube carburetor, means forming a main mixing chamber, means forming a primary mixing chamber opening into said main mixing chamber, a primary air inlet for said primary mixing chamber, a secondary air inlet for said secondary mixing chamber, a fuel jet discharging into said primary mixing chamber, valves for closing said air pas-. sages, and a relief valve carried by one of said valves and adapted to open by suction only when said valves are in closed position.

5. In a carburetor, means forming a main mixing chamber, means forming a primary mixing chamber discharging into said main mixing chamber, means forming a primaryair passage delivering into said primary mixing chamber and a secondary air passage delivering into said secondary mixing chamber, a relief valve, means for interposing said relief valve in the said secondary air passage, and means operated by interposing the relief valve for restricting the primary air passage. i

6. In a carburetor, a main venturi, a standpipe forming a primary mixing chamber and discharging at the throat of said main ven-- turi, said standpipe being smaller than the throat of said venturi and concentric therewith, means for normally admitting air under atmospheric pressure to said standpipe, an annular valve slidably mounted on said standpipe adapted to close against the end of said venturi, and a spring closed valve for controlling said inlet, said valve being adapted .to open under starting suction to admit small quantities of air for low speed operation under low temperature conditions.

7. In a carburetor, a main venturi, a standpipe forming a primary mixing chamber and discharging at the throat of said main venturi, said standpipe being smaller than the throat of said venturi and concentric therewith, means for normally admitting air under atmospheric pressure to said standpipe, a throttle valve for controlling the flow of mixture through said primary mixing chamber, a low speed fuel discharge conduit discharging into said primary mixing chamber at a point adjacent said throttle valve, an annular alve slidably mounted on said standpipe adapted to close against the end of said venturi, a valve for controlling said inlet, and means interconnecting said valves whereby they may be controlled by a single operating means.

8. In a carburetor, a main venturi, a standpipe forming a primary mixing chamber and discharging at the throat of said main venturi, said standpipe being smaller than the throat of said venturi, and concentric therewith, an air inlet for said standpipe, an

annular valve slidably mounted on said standpipe adapted to close against the end of said venturi, a valve for controlling said inlet, and a relief valve carried by one of said valves.

9. In a carburetor, a main venturi, a standpipe forming a primary mixing chamber and discharging at the throat of said main venturi, said standpipe being smaller than the throat of said venturi and concentric therewith, an air inlet for said standpipe, an annular valve slidably mounted on said standpipe adapted to close against the end of said venturi, a valve for controlling said inlet, and a relief valve carried by said firstnamed val e.

10. In a carburetor, primary and secondary air passages, valves controlling said passages, manual operating means directly connected to one of said valves, a spring tending to hold the other of said valves in closed position, and a second spring interposed between said manually operated means and said springheld valve, said second spring being operable by said manually operated means to overcome said first-named spring and to normally hold the spring-held valve in open position.

11, In a carburetor, means forming a mixing conduit having an air inlet and a mixture outlet, choke and throttle valves respectively controlling said inlet and said outlet, means forming a passageway adapted to discharge into said mixing conduit between said valves, means for supplying fuel to said passageway, means for admitting air to said passageway, a valve for controlling said air admitting means, said valve being operatively connected to said choke valve, and means for connecting said choke and throttle valves whereby said throttle valve will be at least partially opened when said choke valve is closed.

12. In a carburetor, means forming a mix-" ing conduit having an air inlet and a mixture outlet, choke and throttle valves respectively controlling said inlet and said outlet, a passageway adapted to discharge into that said part of said mixing conduit between said valves and means for supplying fuel and air to said passageway, a valve controlling the supply of air tosaid passageway, said valve being connected to said choke valve, a relief valve adapted to open under starting suction when said choke valve isclosed to admit air to that part of said mixing conduit betwen the choke and throttle valves.

13. In a carburetor, means forming a mix ing conduit having an air inlet and a mixture outlet, choke and throttle valves respectively controlling said inlet and said outlet, a passageway adapted to discharge into that part of said mixing conduit between said valves and means for supplying fuel and air to said passageway, a valve controlling the supply of air to said passageway, said valve being connected to said choke valve, a relief Valve adapted to open under starting suction when said choke valve is closed to admit air to that part of said mixing conduit between the choke and throttle valves, a low speed fuel conduit discharging into said mixing conduit at a point adjacent said throttle valve.

14. In a carburetor, means forming a mixing conduit having an air inlet and a mixture outlet, choke and throttle valves respectively controlling said inlet and said outlet, a passageway adapted to discharge into that part of said mixing conduit between said valves and means for supplying fuel and air to said passageway, a valve controlling the supply of air to said passageway, said valve being connected to said choke valve, a relief valve adapted to open under starting suction when said choke'valve is closed to admit air to that part of said mixing conduit between the choke and throttle valves, a low speed fuel conduit discharging into said mixing conduit at a point adjacent said throttle valve, and a lost motion connection between said choke and throttle valves, whereby said throttle valve may be operated independent of said choke valve when said choke valve is in open position, but said throttle valve will be at least partially opened when said choke valve is closed.

15. In a carburetor, means forming a mixing chamber, a throttle valve controlling the outlet of said mixing chamber, a choke valve controlling the inlet of said mixing chamber, means forming a constant level supply chamber, a fuel well, means comprising a restricted passageway for supplying fuel from said constant level supply chamber to said well, an upwardly extending nozzle mounted in said well, an air passage for admitting air to said well, a plurality of holes in said nozzle at different levels, said nozzle discharging into said mixing chamber between said throttle and choke valves, a relief valve for admitting air under starting suction to said mixing chamber when said choke valve is closed and an air connection between the upper part of the said constant level chamber and a, point in the mixing conduit anterior to the choke valve.

In testimony whereof, I aflix my signature this 21 day of June, 1929.

LEONARD D. BOYCE. 

